NEW ORLEANS -- Drew Brees said he doesn't know if he will be able to play in Week 11 after he was sidelined by an injury to his ribs at halftime of the New Orleans Saints' 27-13 victory over the San Francisco 49ers on Sunday.

Coach Sean Payton said Brees will have an MRI and X-rays to determine the extent of the injury.

"I'm just taking it one day at a time. I've done that this entire season. And I'll continue to do that. I'm not sure what tomorrow holds," said a somber Brees, who also has been fighting through an injury to his right throwing shoulder in recent weeks. "But you can know I'm gonna do everything I can to be as effective as I possibly can come next week.

"I mean, nothing's a long-term thing. It's just a matter of how long it's gonna be. And honestly, I really don't know. It's not something, quite to this extent, that I've experienced."

Brees, 41, played the final eight minutes of the first half after absorbing a big hit by defensive tackle Kentavius Street. He led the Saints (7-2) to two touchdowns as they rallied from a 10-0 deficit for their sixth consecutive victory.

But Brees said he felt worse after the halftime break, so Jameis Winston played most of the second half in his place.

Winston completed 6 of 10 passes for 63 yards with no touchdowns and no turnovers. Fellow backup Taysom Hill also played one series at QB, running the ball four times for 36 yards with a lost fumble. The Saints' defense and special teams did most of the heavy lifting, with defensive backs Malcolm Jenkins and Patrick Robinson each intercepting passes and undrafted rookie receiver Marquez Callaway recovering two fumbled punt returns.

The Saints have not specified who would replace Brees if he can't start next Sunday's home date with the Atlanta Falcons -- though Winston would appear to be the leading candidate based on his role with the team and the way the Saints used Teddy Bridgewater ahead of Hill in a similar situation last year.

Brees described the rib injury as "a cumulative thing, probably not just one." It wasn't clear if that meant he aggravated a preexisting rib injury. But it was clear that Brees was experiencing discomfort after the hit by Street, which resulted in a questionable personal-foul penalty.

Hill took the next two snaps at quarterback after that play. Brees lined up at receiver on the first play, then went to the sideline for one play to throw the ball and try to get loose.

Brees reentered the game to pitch the ball to running back Alvin Kamara for a 2-yard touchdown. Then, he played the next series, completing five passes during a two-minute drill touchdown drive.

Brees said he "actually felt terrible" before that last drive, but he stiffened up even more during halftime.

"So when I came out in the second half and started throwing the ball, it became really apparent that I wasn't gonna be effective," Brees said. "I can't really describe it other than it was preventing me from doing my job.

"I was not gonna be able to be effective. It had nothing to do with pain. It was definitely just what my body was gonna be able to do or not be able to do."

Brees has missed only six games because of injury in his 20-year NFL career -- five of them in 2019 because of a torn thumb ligament. The Saints went 5-0 in that span with Bridgewater at QB.

"As he came out in the second half, he felt it was really impacting him," Payton said. "His back felt sore as he tried to throw. He just came up to me and said, 'Hey, I don't feel I'm capable of playing.' And so quickly we made the switch, and that happens sometimes.

"He felt strong enough about letting me know. And I know when he does that -- which is probably gonna be the first time in 15 years that it was significant enough that he felt like he couldn't function in the second half."

Winston, who was appearing in just his second game of the season, showed some rust, nearly throwing one interception and missing on a couple of throws in the red zone. But he did lead New Orleans on field goal and touchdown drives -- setting up the latter with a 3-yard run to the 1-yard line.

"I was very comfortable," said Winston, a former No. 1 overall draft pick who spent his first five NFL seasons as a starter for the Tampa Bay Buccaneers. "I was excited that I had a marvelous opportunity. And I just knew that my main job was to go in there and do what Drew would do -- just protect the football and try to lead us down there and score.

"I try to give everybody my all. I try to be right there with Drew along the way, watching film with him, preparing with him. So I felt like I went out there and I was prepared to lead this team. And I'm happy that my teammates had my back and they went out there and executed well and things went our way."

Payton and Brees both complimented Winston for the way he handled himself while jumping into the game midstream.

"Listen, I'm proud of him," Payton said. "He led us to an important scoring drive, led us to another field goal drive. The one thing I would say with Jameis, too, is he's extremely bright. So functioning and understanding what we're doing, he picks it up quickly."

Kamara scored all three of the Saints' touchdowns Sunday, continuing to make his case for NFL Offensive Player of the Year, if not an MVP candidate.

The Saints suffered a number of injuries.

Cornerback Marshon Lattimore left early with an oblique injury, though he also remained dressed on the sideline. Receiver Tre'Quan Smith and tight end Josh Hill were ruled out with concussions. Defensive tackle Malcom Brown left early with a calf injury. Safety C.J. Gardner-Johnson left the field late in the game with an unspecified injury, though he said he was fine afterward. And offensive linemen Terron Armstead and Andrus Peat both briefly left the field with injuries before returning.